Endoscopes for the visual inspection of internal organs of living bodies are well known. They include either a flexible or rigid tube extending between a control housing at the proximal end and a tip or probe at the distal end thereof. A flexible tube portion is included adjacent the probe which is bent under operator control by use of control mechanism at the control housing. Optical illuminating and viewing means are provided which include an objective lens at the probe and an eyepiece at the control housing for use in viewing the cavity surface.
While endoscopes provide the operator with information concerning interior surface conditions, the need for ultrasonic imaging of underlying surfaces has been recognized. In an article entitled A New Trans-digestive-tract scanner with a gastro-fiberscope, by K. Hisanaga and A. Hisanaga, in the Proceedings of the 23rd Annual Meeting of the American Institute of Ultrasound in Medicine, 1978, page 108, an optic-fiber endoscope is shown fitted with a movable transducer for obtaining B-sector-scan images of underlying tissues. However, as noted in the article, the images obtained are of no diagnostic value. Probes containing linear transducer arrays also are known as shown in U.S. Pat. No. 3,938,502 and German Pat. No. 2,305,501. There, circular and rectilinear transducer arrays, respectively are shown. These probes, however, lack optical viewing means which permit the operator to locate the probe at desired locations within the body part. Without such knowledge of transducer location and orientation, any ultrasonic images obtained would be of minimum diagnostic use. Additionally, optical viewing means generally are required for safely guiding the probe during insertion thereof into the body organ to avoid damage and pain to the patient. These probes also lack acoustical cylindrical lens focusing means for beam focusing. Linear array ultrasonic transducers with a cylindrical lens for focusing in one plane normal to electronic beam focusing in a second plane are known as shown in U.S. Pat. No. 3,936,791. There, however, the lens is formed with a concave outer free surface which would not be suitable for use in an endoscopic probe.